Pyridine 1-oxide mass spectra

Klemm and coworkers18a prepared some isomeric chlorinated 2,3-dihydrothieno-[2,3-b]pyridine 1-oxides and reported their El mass spectra at 70 eV. Only one isomer (30) was isolated in the case of the 5-ethyl derivative the mass spectrum of which... 

Dehydroguattescine (117) was found in G. schomburgkiana (50,51). Its spectral properties showed that it resembled guattescine (116) quite closely. Its mass spectrum, however, indicated a molecular weight lower than that of guattescine by 2, and the H-NMR spectrum exhibited a typical pyridine AB system at 7.44 and 8.38 ppm (7 = 6 Hz). These data led to the proposal of structure 117, which received support from its semisynthetic preparation by m-chloroperbenzoic acid oxidation of O-methylbelemine (147) (see below). Dehydroguattescine is the only 7-hydroxy-7-methyl-4,5,6,6a-tetradehydroaporphine known so far. 

The positive ion mass spectra of pyridine Af -unsubstituted N-imines, generated within the ion source by pyrolysis of the corresponding hydrochlorides, have been investigated.133 The mass spectrum of pyridine AMmine contains peaks attributable to the loss of 15 (NH) and 16 (NH2) mass units from the molecular ion in a ratio of approximately 2.5 1, whereas introduction of a methyl group at the 2-position of the pyridine ring causes a significant change in the intensity ratio of the [M — NH]+ and [M — NH2] + ( 1 2.5). This can be attributed to the operation of a so-called ortho effect, as in the case of 2-alkylated pyridine N-oxides. 

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